Evaluation of Anabaena flos-aquae as a precursor for trihalomethane and haloacetic acid formation

This paper summarizes an investigation of a common blue–green algae species, Anabaena flos-aquae, as a precursor substrate in the formation of trihalomethane (THM) and haloacetic acid (HAA) compounds during chlorination. The algae were cultured under controlled and axenic conditions throughout all four growth phases and samples taken during these phases were subjected to chlorination to determine disinfection byproduct (DBP) formation potentials. Algal cells and extracted extracellular organic matter (EOM) of Anabaena showed a comparable ability to form THM and HAA compounds as humic and fulvic acids. Overall yields of total THM (4) and HAA (9) compounds were closely related to the growth phase, with peak formation in the late exponential-stationary phases. Specific (normalized) DBP yields (yield/unit C) were in the range of 2–11 μmol/mmol C for TTHM and 2–17 μmol/mmol C for THAA. The presence of bromide appeared to increase TTHM formation and decrease THAA formation, thereby leading to a shift in the DBP species from HAA to THM compounds. The distribution of HAA species varied with growth phase. Monochloroacetic acid was found to be the dominant HAA species during the lag and early exponential phases, and a prominent compound in the later growth phases.